太赫兹功率探测器高灵敏度调制解调系统设计

针对太赫兹被动成像系统前端功率探测器内部引入的低频噪声（1/f噪声）对成像精度的影响较为明显的问题，设计了一种高灵敏度调制解调系统来降低低频噪声对成像的干扰。通过控制外部信号源使功率探测器在正常工作与饱和状态之间快速切换，实现对目标信号的调制，从而将目标信号的频率调制到高于功率探测器引入的低频噪声频段以便将低频噪声滤除，进而降低该低频噪声对后续成像质量的影响。通过MATLAB软件仿真，可模拟出信噪比(SNR)为31.17 dB的功率探测器输出信号，同时通过对目标信号调制解调，目标信号的信噪比被提高到了268.13 dB。通过对所设计的高灵敏度调制解调系统实际测试，可得目标信号的信噪比由4.22 dB提高到了301.88 dB。研究结果表明，该高灵敏度调制解调系统能有效降低太赫兹探测器内引入的低频噪声对后续成像质量的影响。

Design of high sensitivity modulation and demodulation system for terahertz power detector

Aiming at the problem that the low-frequency noise (1/f noise) introduced in the front-end power detector of the terahertz passive imaging system has a significant impact on the imaging accuracy, a high-frequency modulation and demodulation method is proposed to reduce the interference of low-frequency noise on imaging. By controlling the external signal source, the power detector can quickly switch between normal operation and saturation state to realize the modulation of the target signal, thereby modulating the frequency of the target signal to a frequency higher than the low frequency noise introduced by the power detector in order to filter the low frequency noise. In addition, the influence of the low-frequency noise on the subsequent imaging quality is reduced. The output signal of the power detector with a signal-to-noise ratio (SNR) of 31.17 dB is simulated by MATLAB. After the target signal was modulated and demodulated according to the above method, the signal-to-noise ratio of the target signal is increased to 268.13 dB. In the experiments, the signal-to-noise ratio of the target signal is increased from 4.22 dB to 301.88 dB. The research results show that the high-frequency modulation and demodulation method can effectively reduce the influence of low-frequency noise introduced in the terahertz detector on the subsequent imaging quality.